mm/ksm: convert get_mergeable_page() from follow_page() to folio_walk

Let's use folio_walk instead, for example avoiding taking temporary folio
references if the folio does not even apply and getting rid of one more
follow_page() user.

Note that zeropages obviously don't apply: old code could just have
specified FOLL_DUMP.  Anon folios are never secretmem, so we don't care
about losing the check in follow_page().

Link: https://lkml.kernel.org/r/20240802155524.517137-6-david@redhat.com
Signed-off-by: David Hildenbrand <david@redhat.com>
Cc: Alexander Gordeev <agordeev@linux.ibm.com>
Cc: Christian Borntraeger <borntraeger@linux.ibm.com>
Cc: Claudio Imbrenda <imbrenda@linux.ibm.com>
Cc: Gerald Schaefer <gerald.schaefer@linux.ibm.com>
Cc: Heiko Carstens <hca@linux.ibm.com>
Cc: Janosch Frank <frankja@linux.ibm.com>
Cc: Jonathan Corbet <corbet@lwn.net>
Cc: Matthew Wilcox <willy@infradead.org>
Cc: Sven Schnelle <svens@linux.ibm.com>
Cc: Vasily Gorbik <gor@linux.ibm.com>
Cc: Ryan Roberts <ryan.roberts@arm.com>
Cc: Zi Yan <ziy@nvidia.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

diff --git a/mm/ksm.c b/mm/ksm.c
index 14d9e53b1ec2d88d2bd70dd290db9e7dcfb20b48..742b005f3f77b4a0bc5e892a0475c99b7f3c7870 100644 (file)
--- a/mm/ksm.c
+++ b/mm/ksm.c
@@ -767,26 +767,28 @@ static struct page *get_mergeable_page(struct ksm_rmap_item *rmap_item)
        struct mm_struct *mm = rmap_item->mm;
        unsigned long addr = rmap_item->address;
        struct vm_area_struct *vma;
-       struct page *page;
+       struct page *page = NULL;
+       struct folio_walk fw;
+       struct folio *folio;
 
        mmap_read_lock(mm);
        vma = find_mergeable_vma(mm, addr);
        if (!vma)
                goto out;
 
-       page = follow_page(vma, addr, FOLL_GET);
-       if (IS_ERR_OR_NULL(page))
-               goto out;
-       if (is_zone_device_page(page))
-               goto out_putpage;
-       if (PageAnon(page)) {
+       folio = folio_walk_start(&fw, vma, addr, 0);
+       if (folio) {
+               if (!folio_is_zone_device(folio) &&
+                   folio_test_anon(folio)) {
+                       folio_get(folio);
+                       page = fw.page;
+               }
+               folio_walk_end(&fw, vma);
+       }
+out:
+       if (page) {
                flush_anon_page(vma, page, addr);
                flush_dcache_page(page);
-       } else {
-out_putpage:
-               put_page(page);
-out:
-               page = NULL;
        }
        mmap_read_unlock(mm);
        return page;